Re: Postgresql 9.2 has standby server lost data?

[Paula Price <pj8abug@xxxxxxxxx>]

On Fri, Jun 19, 2015 at 12:01 PM, Adrian Klaver <adrian.klaver@xxxxxxxxxxx> wrote:

On 06/18/2015 05:45 PM, Paula Price wrote:

I have Postgresql 9.2.10 streaming replication set up with log shipping in
case the replication falls behind.  I discovered that the log-shipping had
been disabled at some point in time.  I enabled the log shipping again.

If at some point in time the streaming replication fell behind and the
standby server was not able to retrieve the necessary WAL file(s) from the
primary, would the standby server continue to function normally?  Do I need
to rebuild the standby server?  I have restarted the standby server and it
is up and running with no issues.

Well that seems at odds with it being unable to retrieve the WAL files. This leads to these questions:

1) What makes you think it did not retrieve the WAL files via streaming?

​        

It may not have fallen behind via replication.  We do have standby servers that fall behind, but since we have log-shipping it is not a concern.  On this server, i have no idea how long we were running without log-shipping.  I have no idea how many log files I would have to go through to find out when log-shipping stopped.

My basic question is:

If a standby server falls behind with streaming replication AND the standby server cannot obtain the WAL file needed from the primary, will you get an error from the standby server?  Or does it just hiccup and try to carry on?​

 

2) What does the postgres log show at the time you restarted the standby?

 

​2015-06-18 01:12:41.871 UTC::@:[28168]:2015-06-18 01:12:41 UTC: LOG:  00000: database system was shut down in recovery at 2015-06-18 01:12:14 UTC

2015-06-18 01:12:41.871 UTC::@:[28168]:2015-06-18 01:12:41 UTC: LOCATION:  StartupXLOG, xlog.c:6298

2015-06-18 01:12:41.904 UTC::@:[28168]:2015-06-18 01:12:41 UTC: LOG:  00000: entering standby mode

2015-06-18 01:12:41.904 UTC::@:[28168]:2015-06-18 01:12:41 UTC: LOCATION:  StartupXLOG, xlog.c:6384

2015-06-18 01:12:41.987 UTC::@:[28168]:2015-06-18 01:12:41 UTC: LOG:  00000: redo starts at 867/FDF32E18

2015-06-18 01:12:41.987 UTC::@:[28168]:2015-06-18 01:12:41 UTC: LOCATION:  StartupXLOG, xlog.c:6855

2015-06-18 01:12:42.486 UTC::[unknown]@[unknown]:[28213]:2015-06-18 01:12:42 UTC: LOG:  00000: connection received: host=[local]

2015-06-18 01:12:42.486 UTC::[unknown]@[unknown]:[28213]:2015-06-18 01:12:42 UTC: LOCATION:  BackendInitialize, postmaster.c:3501

2015-06-18 01:12:42.486 UTC:[local]:postgres@postgres:[28213]:2015-06-18 01:12:42 UTC: FATAL:  57P03: the database system is starting up

2015-06-18 01:12:42.486 UTC:[local]:postgres@postgres:[28213]:2015-06-18 01:12:42 UTC: LOCATION:  ProcessStartupPacket, postmaster.c:1792

2015-06-18 01:12:43.488 UTC::[unknown]@[unknown]:[28270]:2015-06-18 01:12:43 UTC: LOG:  00000: connection received: host=[local]

2015-06-18 01:12:43.488 UTC::[unknown]@[unknown]:[28270]:2015-06-18 01:12:43 UTC: LOCATION:  BackendInitialize, postmaster.c:3501

2015-06-18 01:12:43.488 UTC:[local]:postgres@postgres:[28270]:2015-06-18 01:12:43 UTC: FATAL:  57P03: the database system is starting up

2015-06-18 01:12:43.488 UTC:[local]:postgres@postgres:[28270]:2015-06-18 01:12:43 UTC: LOCATION:  ProcessStartupPacket, postmaster.c:1792

2015-06-18 01:12:44.489 UTC::[unknown]@[unknown]:[28327]:2015-06-18 01:12:44 UTC: LOG:  00000: connection received: host=[local]

2015-06-18 01:12:44.489 UTC::[unknown]@[unknown]:[28327]:2015-06-18 01:12:44 UTC: LOCATION:  BackendInitialize, postmaster.c:3501

2015-06-18 01:12:44.489 UTC:[local]:postgres@postgres:[28327]:2015-06-18 01:12:44 UTC: FATAL:  57P03: the database system is starting up

2015-06-18 01:12:44.489 UTC:[local]:postgres@postgres:[28327]:2015-06-18 01:12:44 UTC: LOCATION:  ProcessStartupPacket, postmaster.c:1792

2015-06-18 01:12:44.490 UTC::@:[28168]:2015-06-18 01:12:41 UTC: LOG:  00000: consistent recovery state reached at 868/112AF7F8

2015-06-18 01:12:44.490 UTC::@:[28168]:2015-06-18 01:12:41 UTC: LOCATION:  CheckRecoveryConsistency, xlog.c:7405

2015-06-18 01:12:44.490 UTC::@:[28168]:2015-06-18 01:12:41 UTC: LOG:  00000: invalid record length at 868/112AFB00

2015-06-18 01:12:44.490 UTC::@:[28168]:2015-06-18 01:12:41 UTC: LOCATION:  ReadRecord, xlog.c:4078

2015-06-18 01:12:44.490 UTC::@:[28166]:2015-06-18 01:12:41 UTC: LOG:  00000: database system is ready to accept read only connections

2015-06-18 01:12:44.490 UTC::@:[28166]:2015-06-18 01:12:41 UTC: LOCATION:  sigusr1_handler, postmaster.c:4314

​

  I need to know if the

data integrity has been compromised.

I have run this query to determine the lag time for the standby(in case
this tells me anything):
"SELECT now(), now() - pg_last_xact_replay_timestamp()  AS time_lag;
RESULT:
"2015-06-19 00:40:48.83701+00";"00:00:01.078616"


Thank you,
Paula P

--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx